The present invention relates generally to intralumenal or intravascular catheters used to delivery radiation inside a living body. More specifically, the present invention relates to radioactive perfusion balloon catheters for therapeutic purposes.
Intravascular diseases are commonly treated by relatively non-invasive techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These therapeutic techniques are well known in the art and typically involve use of a guide wire and a balloon catheter, possibly in combination with other intravascular devices. A typical balloon catheter has an elongate shaft with a balloon attached to its distal end and a manifold attached to the proximal end. In use, the balloon catheter is advanced over the guide wire such that the balloon is positioned adjacent a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened.
Vascular restrictions that have been dilated do not always remain open. In approximately 30% of the cases, a restriction reappears over a period of months. The mechanism of this restenosis is not understood. The mechanism is believed to be different from the mechanism that caused the original stenosis. It is believed that rapid proliferation of vascular smooth muscle cells surrounding the dilated region may be involved. Restenosis may be in part a healing response to the dilation, including the formation of scar tissue.
Drug infusion near the stenosis has been proposed as a means to inhibit restenosis. U.S. Pat. No. 5,558,642 to Schweich, Jr. et al. describes drug delivery devices and methods for delivering pharmacological agents to vessel walls in conjunction with angioplasty.
Intravascular radiation, including thermal, light and radioactive radiation, has been proposed as a means to prevent or reduce the effects of restenosis. For example, U.S. Pat. No. 4,799,479 to Spears suggests that heating a dilated restriction may prevent gradual restenosis at the dilation site. In addition, U.S. Pat. No. 5,417,653 to Sahota et al. suggests that delivering relatively low energy light, following dilatation of a stenosis, may inhibit restenosis. Furthermore, U.S. Pat. No. 5,199,939 to Dake et al. suggests that intravascular delivery of radioactive radiation may be used to prevent restenosis. While most clinical studies suggest that thermal radiation and light radiation are not significantly effective in reducing restenosis, some clinical studies have indicated that intravascular delivery of radioactive radiation is a promising solution to the restenosis enigma.
Since radiation prevents restenosis but will not dilate a stenosis, radiation is preferably administered during or after dilatation. European Pat. No. 0 688 580 to Verin discloses a device and method for simultaneously dilating a stenosis and delivering radioactive radiation. In particular, Verin discloses a balloon dilatation catheter having an open-ended lumen extending therethrough for the delivery of a radioactive guide wire.
One problem associated with the open-ended lumen design is that bodily fluids (e.g., blood) may come into contact with the radioactive guide wire. This may result in contamination of the guide wire bodily fluid and require the resterilization or disposal of the radioactive guide wire. To address these issues, U.S. Pat. No. 5,503,613 to Weinberger et al. proposes the use of a separate closed-ended lumen in a balloon catheter. The closed-ended lumen may be used to deliver a radioactive guide wire without the risk of contaminating the blood and without the need to resterilize or dispose of the radiation source.
The closed-ended lumen design also has draw backs. For example, the addition of a separate delivery lumen tends to increase the overall profile of the catheter. An increase in profile is not desirable because it may reduce flow rate of fluid injections into the guide catheter and it may interfere with navigation in small vessels.
Another problem with both the open-ended and closed-ended devices is that radiation must travel through the fluid filled balloon in order to reach the treatment site. While this is not a problem for gamma radiation, it poses a significant problem for beta radiation which does not penetrate as well as gamma radiation. Beta radiation is considered a good candidate for radiation treatment because it is easy to shield and control exposure. In larger vessels (e.g., 0.5 cm or larger), a fluid filled balloon absorbs a significant amount of beta radiation and severely limits exposure to the treatment site.
Other intravascular treatments, including delivery of radioactive radiation have been proposed as a means to prevent or reduce the effects of restenosis. Dake et al. suggest delivering radiation within the distal portion of a tubular catheter. Fischell, in the publication EPO 0 593 136 A1, suggests placing a thin wire having a radioactive tip near the site of vessel wall trauma for a limited time to prevent restenosis. Problems exist in attempting to provide uniform radiation exposure using a point or line source. Specifically, as the radiation varies inversely with the square of distance for a point source and inversely with distance for a line source laying off center near one vessel wall may significantly overexpose the nearby wall while underexposing the further away wall. This is especially critical for beta radiation which is absorbed by tissue and blood at a relatively short distance from the source.
Bradshaw, in PCT publication WO 94/25106, proposes using an inflatable balloon to center the radiation source wire tip. In PCT publication WO 96/14898, Bradshaw et al. propose use of centering balloons which allow blood perfusion around the balloon during treatment. U.S. Pat. No. 5,540,659 to Tierstein suggests use of a helical centering balloon, attached to a catheter at points about the radiation source to allow perfusion through the balloon, between the balloon and radiation ribbon source.
Use of continuous centering balloons, having a beta radiation source within, significantly attenuate the beta radiation when filled with inflation fluid and they may also allow the radiation source to xe2x80x9cwarpxe2x80x9d when placed across curved vessel regions, allowing the balloon to bend but having the central radiation source lying in a straight line between the two ends. Segmented centering balloons may improve the warping problem but may have significant beta attenuation due to blood standing or flowing between the beta source and vessel walls. What remains to be provided is an improved apparatus and method for delivering uniform radiation to vessel interiors to inhibit restenosis. What remains to be provided is an improved perfusion catheter having radiation delivery and drug infusion capabilities.
The present invention includes devices and methods for providing radiation to the interior of human body vessels. Preferred devices include both devices having spaced apart, sparse helical windings and devices having tightly wound, closely spaced helical or spiral windings. Preferred sparsely wound devices include a helical perfusion balloon, having at least one helical strand configured into multiple windings having the windings spaced apart longitudinally. The preferred device includes a balloon assembly disposed at the distal region of a catheter shaft, where the catheter shaft includes an inflation lumen, a radiation wire lumen, and a drug infusion lumen. In the distal region, the radiation wire lumen can be disposed above the shaft, making room for a distal, single-operator-exchange guide wire lumen. The spiral, inflatable windings are laced inside shaft through-holes transverse to the shaft longitudinal axis and preferably off center. Lacing the helical strand through the shaft secures the helical balloon to the shaft. Lacing the strands also provides positions along the shaft in between windings for the placement of drug infusion apertures. Preferred devices include a tubular sheath over the helical balloon and shaft distal region, defining a perfusion lumen outer wall. The sheath preferably is snugly attached to both the exterior contours of the individual helical balloon strand windings and the catheter shaft.
One sparsely wound device includes a closed end radiation tube extending through a substantial portion of the balloon. This device allows for use and re-use of non-sterilized radiation sources with the sterile catheter. Another device includes an open ended radiation tube terminating distally near the proximal end of the balloon and not extending substantially through the balloon. This device allows extension of a radiation wire or source through the balloon, without having a radiation wire tube within the perfusion lumen within the balloon. The open ended radiation wire tube embodiment provides greater perfusion cross-sectional area due to the lack of the additional tube within the perfusion flow area. The open ended embodiment can also provide a smaller, uninflated profile.
In devices supporting drug infusion, drug infusion apertures extend through the catheter shaft distal region between balloon strand windings. The infused drug exits the apertures into the inter-strand spaces outside the tubular sheath and contacts the inside of the enclosing blood vessel wall. The drug can spread around the outside of the perfusion sheath through the spiral shaped spaces created by the helical strand windings underneath the tubular sheath material. The confined space allows concentrated drug delivery against the vessel wall. It is believed the combined radiation and drug delivery can significantly inhibit restenosis.
Preferred tightly wound or closely spaced helix devices include a helical, perfusion balloon, having at least one helical strand configured into multiple windings. The helical balloon adjacent windings are closely spaced or in contact when inflated so as to have insubstantial space separating them. The tight spiral windings or closely spaced windings improve centering of the catheter in the curved or tortuous vascular system due to many more balloon segments than lobed designs. The balloon is capable of being inflated with a gas. Using gas to inflate the balloon results in decreased absorption of radiation by the inflated balloon interior. The passage of beta radiation is especially improved by use of a gas rather than a liquid for inflation. Gas allows beta radiation to pass relatively unhindered from beta source to the balloon wall.
In a first closely spaced helix embodiment, the catheter device is a xe2x80x9csingle operator exchangexe2x80x9d catheter suitable for use with a removable, preferably sheathed, radiation source. A second closely spaced helix embodiment includes an xe2x80x9cover the wirexe2x80x9d catheter suitable for use with a removable, preferably sheathed, elongate radiation source. Yet another closely spaced helix embodiment is a single operator exchange device having a combination use lumen partitioned into sterile and non-sterile portions by a permanent sheath extending within the catheter lumen. A guide wire can be inserted through the sterile portion, and a radiation source can be inserted through the non-sterile portion. Maintaining a non-sterile portion separate from contact with the patient allows for use of non-sterilized or non-sterilizable radiation sources, while abating the risk of infection for the patient. Radiation sources in the sterilized portion can be re-used without sterilization, saving considerable time and expense.
Single operator exchange devices according to the present invention can have a proximal, extended entry lumen. This allows for retracting a guide wire distal portion out of the lumen area used in common by both the guide wire and the radiation source. The extended entry lumen is sufficiently long to allow the guide wire to maintain position within the catheter, when lying within, yet does not interfere with insertion of the radiation source through the length of the catheter.
In use, the above mentioned devices can be used for irradiation only, drug infusion, or for concurrent irradiation, drug infusion, and angioplasty. The devices can be advanced over a guide wire, the guide wire retracted, the balloon inflated and the radiation source inserted. After angioplasty and/or irradiation and/or drug infusion are complete, the radiation source can be retracted, the guide wire advanced, and the catheter retracted over the guide wire while maintaining the wire across the treated area.
The present invention also provides a radiation delivery system that permits the use of an open-ended delivery lumen without the risk of blood contamination and without the need to dispose of or resterilize the radiation source. In addition, the present invention provides a radiation delivery system that permits beta radiation to be delivered through a balloon without a significant decrease in radiation exposure to the treatment site, even in large vessels.
One embodiment of the present invention may be described as a catheter having an open-ended lumen, a radiation source disposed in the open-ended lumen of the catheter and a closed-end sheath surrounding the radiation source. The closed-end sheath prevents blood or other fluids from coming into contact with the radiation source so that blood does not contaminate the radiation source and it may be reused. The catheter may be a balloon catheter and may include a guide wire disposed in the open-ended lumen of the catheter. The open-ended lumen may be a full-length lumen or a partial-length lumen (e.g., a rapid exchange lumen). Preferably, the lumen is centered in the balloon for uniform radiation delivery. The catheter may also include a blood perfusion lumen under the balloon or around the balloon. The open-ended lumen in the catheter may have a reduced diameter adjacent the distal end of the catheter to prevent the radiation source from exiting the lumen. Alternatively, the closed-end sheath may have a ridge which abuts a corresponding restriction in the open-end lumen of the catheter to prevent the radiation source from exiting the lumen.
Another embodiment of the present invention may be described as a method of delivering radiation to a treatment site inside the vasculature of a patient using the radiation delivery system described above wherein the method includes the steps of (1) inserting the catheter into the vasculature of a patient; (2) inserting the radiation source into the closed-end sheath; (3) inserting the radiation source and the closed-end sheath into the lumen of the catheter such that the radioactive portion is positioned adjacent a treatment site; and (4) exposing the vascular wall to radiation from the radiation source. Alternatively, the sheath may be inserted into the catheter before the radiation source is loaded into the sheath. The method may also include the steps of (5) removing the radiation source from the catheter; and (6) removing the catheter from the patient. The catheter may be inserted into the vasculature over a guide wire and the guide wire may be removed from the catheter prior to exposing the vascular wall to radiation.
Yet another embodiment of the present invention may be described as a method of delivering radiation to a treatment site inside the vasculature of a patient using a gas-filled balloon catheter and a radiation source wherein the method includes the steps of: (1) inserting the catheter into the vasculature such that the balloon is adjacent to a treatment site; (2) inflating the balloon with a liquid or gas; (3) inserting the radiation source into the catheter such that the radioactive portion is adjacent to the balloon; and (4) exposing the treatment site to radiation from the radiation source through the gas in the balloon. The balloon may be inflated prior to or subsequent to inserting the radiation source. Preferably beta radiation is used, but other radioisotopes may be employed.